The Windows update focuses on improving security ahead of the company's usual drive to keep technical support calls to a minimum.
The Windows XP security update will turn security options on by default, which means that many users will need to reconfigure their software in order to connect to wireless networks, game servers and even their home networks.
Microsoft faced strong criticism for its slack attitude to security until two years ago, when chairman Bill Gates decided to change the company's software development procedures and make security a top priority. The Service Pack 2 (SP2) is designed to completely change the way Windows XP handles security by automatically turning on the firewall and consolidating the operating system's security functions.
Russ Cooper, chief scientist at risk management specialists TruSecure and editor of the NTBugtraq newsletter, said SP2 will be a "huge step forward" for Microsoft security and represents a "significant shift" in Microsoft's attitude.
But Cooper warns that increased security means more technical support calls: "Turning on the Internet Connection Firewall will cause consumers to not be able to access services they were able to access prior to the SP, such as game servers. This will result in support calls, as the consumer tries to get back what they had prior to SP installation," he said.
"Microsoft has always erred on the side of reduced support calls. Here, they err on the side of security," he said.
Graham Cluley, senior technology consultant for antivirus firm Sophos, applauded Microsoft for making security easier to use but again warned that the number of users requiring technical support was bound to increase significantly: "In the past, they disabled anything that might have caused a technical-support issue. The attitude now is that all of your security is already on, and you only turn off those elements that you don't feel you want--as it should be," he said.
Paul Randle, Windows client product manager at Microsoft, said SP2 will mean fewer support calls, because fewer people will be exposed to threats.
"One of the anticipated benefits of SP2 is that it will actually reduce support calls by better protecting customers from attack. Windows XP SP2 is designed to provide new security tools and better control over security settings, so it is easier and less costly for you to protect your network or your PC," he said.
Additionally, Randle said Microsoft's partners will receive "extensive" training on SP2 so that they will be able to service any additional calls: "By working with a close network of partners and training them on SP2...any additional demand for technical support for SP2 will be met," he said.
Munir Kotadia of ZDNet UK reported from London.